Influence of drying and hydrothermal treatments on the denaturation of corn proteins

Poster (2013, February 08)

Corn (Zea mays L.) is the most abundant cereal grain produced in the world. It also provides a significant amount of protein in human and animal diets. During drying corn grains undergo several ... [more ▼]

Corn (Zea mays L.) is the most abundant cereal grain produced in the world. It also provides a significant amount of protein in human and animal diets. During drying corn grains undergo several alterations including protein denaturation. A series of studies have been conducted in order to understand mechanisms behind denaturation of corn proteins during drying and heat moisture treatments. Using a laboratory fluidized-bed dryer, a flint corn variety have been dried between 54° and 130°C and subjected to different analyses from a qualitative point of view with a sequential extraction of corn protein fractions and from a quantitative point of view with the modeling of salt-soluble proteins using Promatest assay. Albumin, globulin and zein solubilities dropped significantly when the drying temperature increased. The electrophoretic patterns of zein and glutelin-G1 were not significantly modified, although the solubility of zein was affected by the drying temperature. The analysis of the different protein group solubilities suggested that denaturation mechanisms other than the creation of new disulfide bonds occurred during the drying of corn at high temperature. The study of the effect of heat treatments on the extractability of salt-soluble proteins shows that temperature; moisture content and time of processing greatly influence their kinetic denaturation. Modeling of salt-soluble proteins reveals that the evolution of extractible salt-soluble proteins content of corn kernels during drying at high temperature is more correctly described with a second order kinetic reaction. Investigations continue in order to understand protein denaturation and influence in functional properties and end-use of corn protein-based products. [less ▲]

The swelling behaviour of wheat starch granules during isothermal and non-isothermal treatments

in Journal of Food Engineering (2013), 114(2), 199-206

The size of wheat starch granules was measured during isothermal and non-isothermal treatments and fitted using mathematical models in order to elucidate the time–temperatures dependence of the swelling ... [more ▼]

The size of wheat starch granules was measured during isothermal and non-isothermal treatments and fitted using mathematical models in order to elucidate the time–temperatures dependence of the swelling phenomenon and to improve our understanding of the mechanism followed by granules during gelatinization. Upon the onset temperature of gelatinization, starch granules size increase rapidly and tend to reach equilibrium values that depend on the temperature and heating rate applied. The most accurate fitting of granule size observed overall isothermal treatments was obtained with the third-order kinetic and the Weibull empirical models. The activation energy of swelling calculated for isothermal treatment varied between 41 and 318 kJ mol 1, depending on the mathematical model considered. Therefore, without a consensus on the mechanism and order of reaction followed during gelatinization, the meaningful of kinetic parameters calculated using mathematical models seems highly questionable. During non-isothermal treatments at lower heating rate, it seems like a limitation of the swelling capacity of granules was induced. This phenomenon was attributed to restructuration occurred inside of granules. So, forecasting the swelling behaviour of starch granules during non-isothermal treatment has to consider both the time–temperature and the heating rate applied. [less ▲]

Optimizing red sorghum malt quality when Bacillus subtilis is used during steeping to control mold growth

in Journal of the Institute of Brewing (2012), 118(3), 295-305

Previous work having shown that Bacillus-subtilis-S499-based biocontrol treatments applied without aeration at the steeping stage of red sorghum malting offered good mould reduction but yielded malts with ... [more ▼]

Previous work having shown that Bacillus-subtilis-S499-based biocontrol treatments applied without aeration at the steeping stage of red sorghum malting offered good mould reduction but yielded malts with low levels of key hydrolytic enzymes, we attempted to raise these levels by aerating the steeping liquor, varying the steeping time (from 8 to 40 h) and temperature (from 25 to 35°C), and combining a biocontrol treatment with prior steeping in 0.2% NaOH. Aeration proved particularly important whenever B. subtilis cells were present in the steep liquor. The optimal temperatures for α- and β-amylase were 30 and 25°C, respectively. By increasing the steeping time it was possible to improve the α-amylase activity, but the -amylase activity peaked sharply between 16 and 20 h, depending on the steeping medium. A good compromise was steeping in biocontrol medium for 14 to 16 h at 30°C. Combination steeping treatments (0.2% NaOH for 8 h followed by biocontrol for 8 h) yielded malts of a quality approaching that afforded by dilute alkaline treatment. [less ▲]

Influence of drying and hydrothermal treatment of corn on the denaturation of salt-soluble proteins and color parameters

in Journal of Food Engineering (2012), 109(3), 561-570

The effect of heat treatments (drying and hydrothermal treatment) on the extractability of salt-soluble protein (SSP) was assessed using Promatest methodology for corn kernels heated between 60 C and 120 ... [more ▼]

The effect of heat treatments (drying and hydrothermal treatment) on the extractability of salt-soluble protein (SSP) was assessed using Promatest methodology for corn kernels heated between 60 C and 120 C. During drying, the evolution of the grain moisture content is fitted using the analytical solution of Fick equation developed by Crank (1979) for spherical material. The decrease of extractible salt-soluble protein during heating is forecasted using a first and a second order ordinary differential equation. It was found that temperature; moisture content and time of processing greatly influence the kinetic denaturation of SSP of corn kernels. The evolution of extractible SSP content of corn kernels during drying at high temperature is more correctly described with second order kinetic than with the first order kinetic reaction. The Hunterlab color parameters of corn also vary during drying. Lightness and color intensity decrease while yellowness, redness, chroma and hue angle increase through drying time. Most of these Hunterlab color parameters are highly correlated with the salt-soluble proteins content and therefore could be used as indicators of excessive heat treatment and denaturation of salt-soluble proteins in corn kernels [less ▲]

Influence of the processing parameters on the physicochemical properties of puff pastry margarines

Poster (2011, September 18)

Margarinespresentdifferentphysicalpropertieswithrespecttotheirpurposedapplication.Forexample,aspecialtypeoffatisrequiredforpreparationofpuffpastry.Puffpastrymargarines(PPMs)havetobeveryfirmandplastic ... [more ▼]

Margarinespresentdifferentphysicalpropertieswithrespecttotheirpurposedapplication.Forexample,aspecialtypeoffatisrequiredforpreparationofpuffpastry.Puffpastrymargarines(PPMs)havetobeveryfirmandplastic.Therequiredphysicalpropertiesarethusobtainedbyprocessingsuitablyselectedblendsoffatsandoils.Thisstudyfocusesontheinfluenceofprocessingparametersonphysicochemicalpropertiesofpuffpastrymargarine.Forthispurpose,twoselectedfatblendswereconsidered(bothpalm-based):onewaslow-trans(0.5%)andtheotherwastrans-free. [less ▲]

Techniques de séchage des starters lactiques et mécanismes affectant la viabilité cellulaire suite à la lyophilisation

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(2), 287-299

Modelling dehydration and quality degradation of maize during fluidized-bed drying

in Journal of Food Engineering (2010), 100(3), 527-534

At harvest time, maize (Zea mays L.) has a moisture content too high to be stored, and has to be dried. To control the previous termdryingnext term impact on maize characteristics, it is necessary to ... [more ▼]

At harvest time, maize (Zea mays L.) has a moisture content too high to be stored, and has to be dried. To control the previous termdryingnext term impact on maize characteristics, it is necessary to accurately know the spatial distribution of temperature and moisture content in the kernel, and the kinetics of quality loss in relation to these two factors. To this end, a physical model of heat and mass transfer in a maize kernel was designed. The Fick and Fourier equations were solved by the finite element method (FEM). The real 3D geometry of maize was obtained by NMR imaging and then used to build the mesh needed for the FEM computations. The model correctly describes the evolutions of maize moisture and salt-soluble protein content during fluidized-bed previous termdryingnext term with a constant previous termdryingnext term air temperature between 50 °C and 100 °C. [less ▲]

Comparative study of the effect of drying temperatures and heat-moisture treatment on the physicochemical and functional properties of corn starch

in Carbohydrate Polymers (2010), 79(3), 633-641

This manuscript compares the modifications induced by the heat-moisture treatment of native starch (HMT) and by the hot-air drying of corn on wet-milled starch granules. High temperatures applied during ... [more ▼]

This manuscript compares the modifications induced by the heat-moisture treatment of native starch (HMT) and by the hot-air drying of corn on wet-milled starch granules. High temperatures applied during both corn drying and HMT reduced the swelling capacity of granules, increased the starch gelatinization temperatures and decreased their residual enthalpy. Pasting behaviour of pre-treated starch showed a decrease of peak and breakdown viscosity when corn drying and HMT temperatures increased. Microscopic analysis showed that after hydrothermal treatment, starch granules extracted from corn dried at lower temperature swell more significantly than those extracted from corn dried at higher temperature. All these changes suggest the occurring of structural modifications within starch granules during high-temperature pre-treatments. At similar temperatures and initial moisture contents, HMT affected the physicochemical and functional properties of cornstarch more dramatically than hot-air drying. Differences induced by these two treatments were attributed to the availability of water around granules during these two pre-treatment procedures. [less ▲]

Sensitivity analysis of a 3D diffusive drying model

Poster (2009)

Influence of drying temperature on the wet-milling performance and the proteins solubility indexes of corn kernels

in Journal of Food Engineering (2009), 95

The effects of air drying temperature on the wet-milling performance and the proteins solubility indexes were investigated for corn kernels dried between 54°C and 130°C. It was observed that when the ... [more ▼]

The effects of air drying temperature on the wet-milling performance and the proteins solubility indexes were investigated for corn kernels dried between 54°C and 130°C. It was observed that when the drying temperature increases, the starch yield drops significantly. The gluten recovered increased abruptly for drying temperatures up to 80 C. The albumin, globulin and zein solubility indexes decreased continuously when corn drying temperatures increased. According to the temperatures used, the starch yield, the gluten recovered and the salt-soluble proteins solubility indexes were adjusted satisfactorily by using a two asymptotic logistic model. This model has the advantage of supplying information on the dynamic of the variation of described parameters. The solubility index of total salt-soluble proteins was shown to be a suitable indicator of the severity of the drying treatment in regard to the corn wet-milling performance. [less ▲]